You can try contacting someone in Mattamy's customer service department and asking if they can send you a copy. We just moved into a resale Mattamy house and I sent an email to customer service asking how I go about obtaining a floor plan for our model. I received a quick response and a copy of the floorplan was sent to me in the mail.

I didn't think of trying that. In the past I've asked for floorplans of a few models that aren't currently for sale, and the sales office said No, that they can't give out floor plans for houses they aren't currently selling. But yeah, maybe if you call them and say you just bought a resale mattamy home, they'll be more courteous and give you a copy.